The present invention relates to technology for manufacturing semiconductor devices and, particularly, to technology for manufacturing semiconductor devices in which a semiconductor pellet is mounted on one main surface of a wiring substrate and is sealed with a resin. The semiconductor devices have many pins are small in size and are cheaply constructed.
In modern packages having an increasingly large number of pins and in which leads are taken out from the peripheries thereof as represented by quad flat packages (QFP) and tape carrier packages (TCP), there is a tendency to shorten the pitch among the leads. However, this imposes a limitation on the production of packages by machining lead frames. In order to cope with this problem, there has been proposed a ball grid array (hereinafter referred to as BGA) which is a surface mount-type package having external terminals disposed on the entire main surface of the package enabling the number of pins to be increased without increasing the size of the package.
The BGA is provided with a wiring substrate having a plurality of electrodes which are formed on the front surface and on the back surface thereof and are electrically connected to each other. A semiconductor pellet is bonded to the front surface of the wiring substrate, the electrodes on the front surface of the wiring substrate and external terminals (pads) of the pellet are electrically connected together via wires that are bonded thereto, and the semiconductor pellet, bonded wires and the electrodes on the front surface are molded with a resin. On the back surface of the wiring board are further formed solder bump electrodes.
The BGA has been disclosed in, for example, "VLSI Packaging Technology (Vol. II)" published by Nikkei BP Co., May 31, 1993, pp. 173-178, U.S. Pat. No. 5,216,278 and U.S. Pat. No. 5,148,165.